【作者】 黄丹丹；

【导师】 董威； 陈勇；

【作者基本信息】 上海交通大学 ， 动力工程及工程热物理， 2019， 硕士

【摘要】 宽弦风扇叶片广泛用于大涵道比涡扇发动机,是发动机最前端部件,提供发动机80%左右的推力。与传统钛合金宽弦风扇叶片相比,复合材料宽弦风扇叶片具有质量轻、噪声低、抗颤振、抗损伤、抗冲击和维护价格低等优点,代表了风扇叶片技术的发展方向。风扇叶片在工作中会受到来自进气道的外界激励和内部流场的激励,复杂的气动载荷会对风扇叶片施加多模态阶次的激励。叶片振动对发动机的稳定性和可靠性有很大的影响,而国内对航空发动机复合材料风扇叶片的振动特性研究较少。压电纤维复合材料(Macro Fiber Composite,MFC)是一种耐损伤、柔韧性好、可靠性好且随时可用的激振器,具有优异的平面驱动性能,且输出响应快、激励频率范围大。本文围绕多MFC模态测试方法和复合材料风扇叶片在MFC复杂激励下的振动特性进行了以下研究工作:1.设计和搭建了多MFC模态测试系统,借助扫描式激光测振仪测量叶片振动响应,并与有限元结果、敲击法实验结果比较。研究结果表明,MFC激振方法操作简单、信噪比较高,可以准确获取叶片的模态参数。为了尽可能激励多且明显地激励出叶片的模态,应将MFC布置于叶片上模态应变较大的位置。不同位置的MFC激励叶片,叶片各阶模态响应有差异。MFC激励下的叶片响应幅值与激励位置处的的叶片模态应变大小和MFC压电纤维方向有关。2.结合坎贝尔图,研究了MFC多模态叠加激励下的复材叶片的振动特性。实验结果表明,多模态叠加激励下的叶片振动响应幅值与叠加前单个频率叶片响应幅值之间是线性叠加关系,叠加系数和模态阶次有关。3.采用MFC驻频激励,研究了倍频激励对叶片振动的影响。实验结果表明倍频对叶片的响应幅值影响不可以忽略,在设计风扇叶片时,由于低阶模态的倍频接近叶片固有频率,前五阶固有频率不应存在倍数关系。4.研究了MFC的不同激励信号间的相位差对风扇叶片振动特性的影响。激励信号之间的相位差对风扇叶片振动幅值的影响与模态阶次和MFC激励处的叶片应变有关;通过调节MFC的位置和激励信号的相位,对叶片可以起到减振的作用。本文多MFC激振叶片的研究结果给叶片的振动测试方法提供了一种新的思路,对进一步研究叶片复杂激励下的振动特性的研究有参考意义。更多还原

【Abstract】 Wide-chord fan blades are widely used in large bypass-ratio turbofan engines,which are the most front-end components of large bypass-ratio turbofan engines and providing 80% propulsion.Compared with the traditional titanium fan blade,composite fan blades are characterized by light weight,low noise,anti-flutter,high efficiency.They also have strong flutter resistance,damage resistance,shock resistance and low maintenance cost,which represent the development direction of fan blades.In operation,the fan blades are excited by the external excitation from the air inlet and the internal flow field of the fan stage during operation.The complex loads will exert multi-frequency component and multi-mode excitations on the fan blade.The vibration of fan blades have great influence on engine stability and reliability.However,interiorly there are few researches on the vibration characteristics of aero-engine composite fan blades.MFCs are characterized by good damage resistance,flexibility,reliability and be on hand.They have excellent plane driving performance,fast output response and wide excitation frequency range.In this paper,the muti-MFCs modal test method and the vibration characteristics of composite fan blades under multi-MFCs complex excitation were studied as follows:1.The multi-MFCs modal test system was designed and constructed.With the scanning laser vibrometer,the vibration response of the concerned points on the blade was measured.Experimental results show that the MFC excitation method is simple to operate and has high signal-to-noise ratio.In order to excite the blade modes as much as possible and obviously,the MFC should be placed at the position where the modal strain of blade is large.With the different placements of the MFC,the modal responses of the blades are significantly different.The response size of the blade is related to the piezoelectric fiber polarization direction strain,and the direction of MFC fiber polarization.2.Combined with the Campbell diagram,the vibration characteristics of composite fan blade under multi-MFCs superposition excitation was studied.There is a linear relationship between the vibration amplitudes of the blades before and after superposition,the superposition coefficients related to the modal order.3.To study the effect of the harmonic excitation on blade vibration,the experiment used a single MFC shaker to perform the sinusoidal excitation.The results show that the effect of harmonics excitation on the response amplitude of the blade cannot be negligible.In the design of fan blades,since the frequency multiplication of low-order modes is close to the natural frequency of the blades,the low orders natural frequency should be avoided to have an evident multiple relationship.4.To study the influence of the excitation signal phase difference of different exciters on the vibration characteristics of the fan blade,MFC shakers are performed to the sinusoidal excitation with different phase.The influence of the phase of the excitation on the vibration amplitude of the fan blade is related to the mode order and the strain at the position of the MFC exciter.By arranging the position of the MFC and adjusting the phase of the MFC excitation signal,the vibration damping effect can be achieved.This paper provides a new way of measuring the vibration of the blade.The results will be used to further study the vibration characteristics of the blade under complex excitation.更多还原